The standard about compact discs (CD), which have been widely used, is referred to as compact disc audio (CD-DA) and based on the description of a standard specification book called Redbook. Based on the specification, various formats for example CD-ROM have been standardized and so-called CD family has been set forth. In the following description, CD generally refers to discs of various formats included in the CD family.
A technology of which a laser beam is irradiated on a properly selected reflective film on a disc and thereby the lengths of pits are varied has been proposed. This recording process is sometimes referred to as additional recording process. When data is additionally recorded on the reflective film, for example identification information that identifies each disc can be recorded. When identification information is recorded in the CD format, a sub code of Q channel of the CD format can be used.
In a CD, an error correction code referred to as CIRC (Cross Interleave Reed-Solomon Code) is used. Thus, when data such as disc identification information is recorded on a reflective film, data that is additionally recorded is detected as an error and corrected with the CRIC. In this case, original data of which the additional recording process has not been performed is read. If the error that exceeds the error correction performance of the CIRC takes place, the error cannot be corrected and data cannot be read. Alternatively, data that has been additionally recorded cannot be read because an interpolating process is performed. Thus, so far, the proposed additional recording process has been performed for only an area in which the error correction code encoding process is not performed. Thus, the applicable range of the additional recording process is restricted.